Method for stressing and anchoring wires of a bundle of tension wires

ABSTRACT

A method of stressing and anchoring the wires of a bundle or bunch of tensioning wires or the like for a concrete structure by means of clamping wedges and an anchoring body, which comprises the steps of loosely placing an anchoring head equipped with wire receiving bores onto the wires while the wires are in untensioned condition. Clamping wedges are inserted into the wire receiving bores and are fixedly retained therein without the wedges clamping the wires. The anchoring head together with the thus inserted wedges is displaced along the wires into a recess of the concrete structure accommodating the ends of the wire bunch, displacement occurring through a distance approximately corresponding to the length of elongation of the wires which is contemplated. Then in this position of the anchoring head the clamping wedges are pressed against the untensioned wires into a wire clamping position, the wire bunch is tensioned, tensioning or stressing occurring during withdrawal of the anchoring head from the concrete structure recess, whereupon the withdrawn anchoring head is supported against the concrete structure.

United States Patent r Brandestini 51 Jan. 16, 1973 [54] METHOD FORSTRESSING AND ANCHORING WIRES OF A BUNDLE OF TENSION WIRES [76]Inventor: Antonio Brandestini, 60 Alte Landstrasse, Zurich, Switzerland22 Filed: April 1, 1971 21 Appl.No.: 130,103

[30] Foreign Application Priority Data May 25, I970 Switzerland..7724/70 [52] US. Cl ..29/452, 29/DIG. 42 [51] Int. Cl. ..B2ld 39/00[58] Field of Search ..29/452, DIG. 42, 155

[56] References Cited UNITED STATES PATENTS 3/1945 Fregssinet ..29/452 X1/1956 Birkenmaier et a] ..29/452 Primary Examiner-Thomas I-I. EagerAttorney-George F. Dvorak, Stephen T. Skrydlak and Marden S. Gordon [57]ABSTRACT is displaced along the wires into a'recess of the concretestructure accommodating the ends of the wire bunch, displacementoccurring through a distance approximately corresponding to the lengthof elongation of the wires which is contemplated. Then in this positionof the anchoring head the clamping wedges are pressed against theuntensioned wires into a wire clamping position, the wire bunch istensioned, tensioning or stressing occurring during withdrawal of theanchoring head from the concrete structure recess, whereupon thewithdrawn anchoring head is supported against the concrete structure.

10 Claims, 5 Drawing; Figures BACKGROUND OF THE INVENTION ferentproposals for stressing and anchoring of tensioning cables consisting ofa number of wires or strands, by means of clamping wedges and anchoringbodies. In most of these state-of-the-art proposals the wires or strandsare stressed individually or in bunches through bores in a stationaryanchoring body or head through the action of the tensioning device, andthereafter are anchored by wedges.

This technique which is nowadays conventional possesses a series ofdrawbacks, of which the most important ones will be considered brieflyhereinafter:

The wires or strands of the bundle which is to be stressed or tensionedare nested together or forced together within a sleeve along the entirelength of the concrete structure. However, at the ends of the bundle theindividual wires of such bundle must be spread apart owing to therequired spacing between the individual bores of the anchoring headfixedly arranged at the end of the concrete structure, these boresserving to receive the clamping wedges. This spreading of the individualwires of the bundle is required to allow such wires or strands, duringthe tensioning or stressing thereof, to be pressed in the direction ofthe bundle axis against the walls of the bores. It should be evidentthat it is difficult to insert the clamping wedges with sufficient careinto the conical bores, not only because the wires or strands arearranged eccentrically within the bores, but also because they aretightly stressed or tensioned. It is practically impossible to cleanlyinsert the wires without forcing them, even if each wedge set for eachwire or strand is hydraulically inserted or pressedin. This is apartfrom the fact that such individual insertion or pressing-in operationsfor the sets of wedges, at

best, is only possible in practice when stressing individual wires orstrands. Thus the danger exists that the individual wires or strandswill be damaged by the teeth of the wedges and furthermore will not beproperly anchored, so that during lowering of the tensioning deviceindividual ones of these wires or strands will slide, something which isdifficult to control.

Further, in connection with the above it might be indicated thatproposals have been made for reducing the eccentricity of the wires orstrands in the bores which contemplates extending the conical portion ofeach bore hole in which the wedges come to rest in a direction towardsthe center of the bundle by means of a cylindrical bore which is asnarrow as possible. However, it must be indicated that this cylindricalportion of the bore cannot be so narrow that the wire or the strand iscorrectly centrally guided, since the introduction, especially of anumber of strands and the displacement of the anchoring head along thestrands in its fixed position at the end of the concrete structure mustbe able to be carried out with the least possible friction. There isstill however a further reason which opposes narrowing of the boreholes, namely: during cutting of the wires or strands there appearthreads or the like at the ends which protrude and render more difficultthe threading-in or insertion into the bores of the anchoring head. Itis also for this reason that a relatively larger diameter of the boresmust be provided, so that, as stated above,'

a faultless centering of a wire or strand is no longer ensured for.

SUMMARY OF THE INVENTION Therefore, there is still present a real needin the art for a technique of stressing and anchoring the wires orstrands of a wire bunch which is not associated with the aforementioneddrawbacks of the prior art proposals. Hence, a primary object of thepresent invention is the provision of a method for stressing andanchoring the wires or the like of a bunch of wires which is notassociated with the aforementioned drawbacks of the prior art and whicheffectively and reliably fulfills the existing need in the art.

Now, in order to implement the above objects of the invention, as wellas others which will become more readily apparent as the descriptionproceeds, the method aspects of this invention contemplate looselyplacing upon the untensioned tensioning wires of the bunch an anchoringhead provided with bores for receiving the wires, inserting wedges andretaining such wedges at the bores of the anchoring head which form thewedge seating surfaces without clamping the wires. Then the anchoringhead together with the wedges which have been inserted in this mannerare displaced back in the recess of the concrete structure receiving thewire ends along the wires through a distance approximately correspondingto the contemplated length of elongation of the wires, and in thisposition of the anchoring head the wedges are pressed against the stilluntensioned wires into a clamping position, then the wire bunch orbundle is tensioned, so that the anchoring head which is now fixedlyclampedat the wires is pulled out of the recess and supported at the endof the concrete structure.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be betterunderstood and objects other than those set forth above, will becomeapparent DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Describingnow the drawings, in FIG. 1 there is schematically illustrated the mostimportant procedural steps performed in the practice of the methodaspects of this invention during stressing and anchoring the wires of abunch or bundle of tensioning wires at a concrete structure by means ofclamping wedges and anchoring body.

It may be assumed that the tensioning wire bundle 1 consists of, forinstance, twelve individual wires or strands. This wire bundle 1 isguided in the usual manner within a tubular sleeve 3 through theconcrete structure 2. Now for the purpose of anchoring these wires ofthe tensioning wire bundle 1 the individual wires thereof, wherein forconvenience in illustration there has only been shown two of themdesignated at reference characters 1a and lb, must be spread apart. Thisspreading apart of the individual wires or strands occurs within acylindrical tube 4 arranged within an appropriately configured recess oropening, which has not been particularly referenced, of the concretestructure 2, and which cylindrical tube 4 is connected via a cone 5 withthe tubular sleeve 3.

Now for the purpose of stressing and anchoring the wires la, 1b which,as shown, extend somewhat past the end face of the concrete structure 2,initially an anchoring head 6, equipped with the receiving bores orapertures 7 for the wires, is pushed onto these wires over the endsthereof. While the anchoring head 6 is still located outside of theregion of the substantially cylindrical tube 4 the wedges 8, 8, providedfor each of the wires la, 1b and so forth, are inserted into theconically widening portion of the associated bores 7. A wedge retainingor holder plate 9, which is similarly provided with the same number ofholes as there are bores 7 at the anchoring head 6, is then temporarilyplaced at such distance over the wedge heads at the anchoring head 6that the individual wedge members 8, 8, for instance three such wedgemembers being provided for each wire, are retained in the bores 7 of theanchoring head 6 and which bores 7 provide wedge seating surfaces, insuch a manner that the wedges themselves do not yet fixedly clampagainst the individual associated wires or strands. This has beenparticularly well shown in FIG. la.

Then the anchoring head 6 together with the loosely inserted wedges 8,8' and also together with the thus mounted wedge retaining plate 9 aredisplaced back along the wires 1a, lb into the tube or conduit 4 toassume the position illustrated in FIG. 1b, this displacement beingequal approximately to the contemplated elongation length of the wires.The transition location between the tube 4 and the cone 5 can thus, forinstance, advantageously serve as fixed stop means. In this position ofthe anchoring head 6 the wedges 8, 8' are placed into their wireclamping position by pressing the wedge retaining plate 9 against theanchoring head 6. The wedge retaining plate 9 then serves to hold thesewedges 8, 8' in their wire clamping position. The pressing or contactingof the wedge retaining plate 9 against the anchoring head 6 can beundertaken from the outside, for instance by tightening screws 10 orequivalent expedients, for instance for such screws being provided foreach plate. Now a wire tensioning head or wire stressing head 11 can besecured to the ends of the wires 10 and lb. This tensioning head 11 canbe constructed, for instance, similar or identical to the actualanchoring head 6, and the attachment of such tensioning head to thewires can likewise be undertaken by wedges 12, 12' and the wedgeretaining or holder plate 13. A tensioning device 14 is then secured Itensioning head 11. Thereafter the actual stressing or tensioningoperation for the wires is performed so that these wires elongate overthe contemplated length, and by virtue of which the anchoring head 6fixedly clamped to the wires is again withdrawn out of the tube 4 intothe position depicted in FIG. 10.

In this position the anchoring head 6 is now supported at the end of theconcrete structure 2, which for instance can be achieved by means of twosemi-ringshaped support plates 16 and 17. Instead of using these supportplates it would also be possible to use a non-illustrated nut memberwhich previously has been mounted and which engages with the anchoringhead via an external threading provided at the anchoring head.

Now the tensioning device 14 can be lowered and removed. The protrudingwire ends are then cut and the entire wire bundle or bunch, as bestshown by referring to FIG. 1d, is then fixedly and securely anchored atthe end region of the concrete structure 2 through the use of the wedgesand the anchoring head. The wedge retaining plate 9 can be, of course,also removed and again used.

The anchoring arrangement shown in FIG. 1d and in FIG. 2 on an enlargedscale is simple to produce and, in contrast to previously fabricatedanchor arrangements considerably safer, and this is especially sobecause the wedges 8, 8' prior to stressing or tensioning of theindividual wires could be placed into their clamping position.

As already indicated above, FIG. 2 illustrates on an enlarged scale thefinished anchoring arrangement for the wires as depicted in FIG. 1d. Byreferring to this Figure it will be recognized that the effective faceof the wedge retaining plate 9 is covered with a rubber plate 18 capableof accommodating possible irregularities appearing on account of thesize of the wedges, the wire diameter, and so forth.

While there is shown and described present preferred embodiments of theinvention, it is to be distinctly understood that the invention is notlimited thereto but may be otherwise variously embodied and practicedwith the scope of the following claims. Accordingly,

What is claimed is:

1. A method of stressing and anchoring the wires of a bunch oftensioning wires or the like for a concrete structure by means ofclamping wedges and anchoring body, comprising the steps of:

a. loosely placing an anchoring head equipped with wire receiving boresonto the wires while in untensioned condition;

. inserting clamping wedges into the wire receiving bores and fixedlyretaining such inserted wedges in said receiving bores without thewedges clamping the wires;

0. displacing the anchoring head together with the thus inserted wedgesalong the wires into a recess of the concrete structure accommodatingthe ends of the wire bunch through a distance approximatelycorresponding to the contemplated elongation of the wires;

. then in this position of the anchoring head pressing the wedgesagainst the still untensioned wires into a wire clamping position;

e. tensioning the wire bunch, while withdrawing from the recess of theconcrete structure the anchoring head fixedly clamped to the wires; and

f. supporting the thus withdrawn anchoring head against the concretestructure.

2. The method as defined in claim 1, including the step of fixedlyretaining the inserted wedges against wedge seating surfaces of the wirereceiving bores.

3. The method as defined in claim 1, further including the step ofutilizing mechanical holding means associated with the anchoring headand operable from externally of the concrete structure for fixedlyretaining the wedges in a loose arrangement in the wire receiving boresand for pressing the wedges into their wire clamping position.

4. The method as defined in claim 1, wherein the anchoring head togetherwith the therein loosely inserted wedges is displaced into the recess ofthe concrete structure along the wires until impacting against a stopwithin such recess, so as to then bring the wedges into their wireclamping position. a

5. The method as defined in claim 1, including the step ofusing asupport element engaging with the anchoring head to support suchanchoring head against the end of the concrete structure.

6. The method as defined in claim 5, wherein there is used support platemeans as such support element.

7. The method as defined in claim 5, wherein there is used nut membermeans as such support element.

8. The method as defined in claim 3, further including the step of usingas the holding means for the wedges an elastically padded-wedge holderplate.

9. The method as defined in claim 8, including the step of temporarilyplacing the wedge holder plate at such a distance over the wedges at theanchoring head after insertion of the wedges that the wedges remainseated in the wire receiving bores without clamping the wires, andfollowing displacement of the anchoring head into the concrete structurerecess reducing the aforesaid distance between the wedge holder plateand the anchoring head such that the wedges are pressed into contactwith the wires.

10. The method as defined in claim 3, further including the step ofremoving the wedge holding means for reuse thereof following step (f)where the anchoring head is supported against the concrete structure.

1. A method of stressing and anchoring the wires of a bunch oftensioning wires or the like for a concrete structure by means ofclamping wedges and anchoring body, comprising the steps of: a. looselyplacing an anchoring head equipped with wire receiving bores onto thewires while in untensioned condition; b. inserting clamping wedges intothe wire receiving bores and fixedly retaining such inserted wedges insaid receiving bores without the wedges clamping the wires; c.displacing the anchoring head together with the thus inserted wedgesalong the wires into a recess of the concrete structure accommodatingthe ends of the wire bunch through a distance approximatelycorresponding to the contemplated elongation of the wires; d. then inthis position of the anchoring head pressing the wedges against thestill untensioned wires into a wire clamping position; e. tensioning thewire bunch, while withdrawing from the recess of the concrete structurethe anchoring head fixedly clamped to the wires; and f. supporting thethus withdrawn anchoring head against the concrete structure.
 2. Themethod as defined in claim 1, including the step of fixedly retainingthe inserted wedges against wedge seating surfaces of the wire receivingbores.
 3. The method as defined in claim 1, further including the stepof utilizing mechanical holding means associated with the anchoring headand operable from externally of the concrete structure for fixedlyretaining the wedges in a loose arrangement in the wire receiving boresand for pressing the wedges into their wire clamping position.
 4. Themethod as defined in claim 1, wherein the anchoring head together withthe therein loosely inserted wedges is displaced into the recess of theconcrete structure along the wires until impacting against a stop withinsuch recess, so as to then bring the wedges into their wire clampingposition.
 5. The method as defined in claim 1, including the step ofusing a support element engaging with the anchoring head to support suchanchoring head against the end of the concrete structure.
 6. The methodas defined in claim 5, wherein there is used support plate means as suchsupport element.
 7. The method as defined in claim 5, wherein there isused nut member means as such support element.
 8. The method as definedin claim 3, further including the step of using as the holding means forthe wedges an elastically padded-wedge holder plate.
 9. The method asdefined in claim 8, including the step of temporarily placing the wedgeholder plate at such a distance over the wedges at the anchoring headafter insertion of the wedges that the wedges remain seated in the wirereceiving bores without clamping the wires, and following displacementof the anchoring head into the concrete structure recess reducing theaforesaid distance between the wedge holder plate and the anchoring headsuch that the wedges are pressed into contact with the wires.
 10. Themethod as defined in claim 3, further including the step of removing thewedge holding means for reuse thereof following step (f) where theanchoring head is supported against the concrete structure.